changing time of schedule block

Hi,
I'm working in so machine basic v1.5 and I'm wondering if it is possible to change the start time and stop time in a schedule block with a %MW. So is there a possibility to for example say %CH0.??? := %MW5 in an operation block? And is there a page where u can see al the possible codes. I already discovered that %TM0.P changes its preset but i don't find a list of al those possibility's.